1. Field of the Invention
This invention relates to an apparatus for viewing scrambled or unscrambled television signals, and more particularly, is directed to an apparatus which records scrambled or unscrambled television signals and which automatically descrambles recorded scrambled television signals when they are reproduced for viewing.
2. Description of the Prior Art
A television broadcasting system is known in which a broadcasting station transmits a scrambled television signal and the consumer or subscriber receives the signal and descrambles or decodes it by means of a decoder supplied by the broadcasting company in return for a fee.
One example of this kind of scrambled television signal broadcasting system provides a broadcast video signal which is inverted in polarity for a certain period of time. In another example, the polarity of the video signal, as broadcast, is changed in a predetermined order or sequence for a certain period of time. In both cases, a corresponding key code is broadcast for use in a decoder at the receiver for descrambling the signals.
There has been proposed a system in which a scrambled broadcast signal is received and recorded directly in a video tape recorder (VTR). The recorded signal is later played back or reproduced and then descrambled in a decoder for viewing. In this system, the scrambled signals can be broadcast during times other than usual broadcast hours or programming time, for example, after midnight, and the signal is then recorded automatically using a timer. In case an ordinary or unscrambled television signal is recorded, such signal, when being reproduced, bypasses the decoder and is displayed on a television monitor. The decoder in such known system includes a switch to select the signal which is to be supplied to the television monitor. The switch must be manually operated so that a standard or unscrambled television signal is supplied to the television monitor. This arrangement is particularly inconvenient to the viewer, however, since the switch must be changed each time there is a change in the program to be viewed between a scrambled television signal and a standard television signal.